The main drawback to him dying immediately was that you couldn't take him back to bear witness to what went on and the fact that he was an elf. However, you can support the Dalish clan that claim he was one of them and if Cassandra is with you she agrees that the truth should be known, which is even better if she is Divine.
For me the main thing about Ameridan was his relationship to Drakon and the way he could reconcile Dalish beliefs with those of the Maker and Andraste. It was tragic that his voice was lost from debate in the Dales as it would seem the isolationist lobby won the day thereafter. It was no surprise that his race and beliefs were removed from the record by the Chantry; just another elven hero who was inconvenient to politics. However, in his memories he seems to anticipate even Drakon eventually coming into conflict with him since he says that Drakon wants to keep things simple with regard to faith had thus has no room in his "vision" for alternative believes even when reconciled with his own. If Drakon was so concerned about the possibility of attack by barbarian hordes led by a dragon, you think he might have followed up on events in the south, even if he was predominately focussed on the Blight. So I think no matter how good friends they were, he was actually quite relieved when no dragon materialised but Ameridan also did not return.
He was an interesting voice from the past but I doubt he would have enjoyed living in the present; it would either have broken him to see what had become of the Dales or turned him into a vengeful monster. Best let him die in relative peace.
Incidentally, I doubt he and Abelas would have got on at all, particularly if Abelas had spouted the line about "You are not of my People". Mind you, the ensuing conflict, whether verbal or physical, might have been interesting.